by Dave Mosher, Skye Gould and Jenny Cheng May 21, 2018 (businessinsider.com)
• Scientists think Europa’s ocean might even be habitable to alien life. Jupiter’s icy moon (about the size of Earth’s moon) is hiding an enormous ocean of saltwater. If all of Earth’s water were combined into one, it would be only half as large as Europa’s liquid reservoir.
• “If there’s life at Europa, it’d almost certainly be an independently evolved form of life,” Bob Pappalardo, a planetary scientist at NASA’s Jet Propulsion Laboratory. “Discovering extraterrestrial life would revolutionize our understanding of biology.”
• This Article compares the volume of water on Earth with the volume of water/ice on these other moons and planetoids in the solar system as a precursor for the possibility of sustaining extraterrestrial life. While Enceladus and Dione hold less water than the Earth, Europa, Pluto, Triton, Callisto, Titan, and Ganymede all hold quite a bit more than the Earth.
• Mimas, a moon of Saturn, and Ceres, the largest asteroid in the solar system, might also have subsurface oceans. But scientists aren’t yet sure how big each one might be, if they exist at all.
• Earth – The Earth harbors about 1.335 ZL of water, according to the National Oceanic and Atmospheric Administration. ZL (zettaliters) equals 1 billion cubic kilometers.
• Enceladus – Enceladus is a relatively small moon of Saturn, at just 314 miles in diameter — about as wide as the state of Arizona. It holds 0.04 ZL of water/ice. (Enceladus hold about 3% of the Earth’s volume of water). But its ocean sprays water into space. NASA’s Cassini spacecraft confirmed the ocean’s existence after its arrival in 2004, later detecting and flying through the water plumes to “taste” them.
• Triton – Triton is a moon of Neptune that’s some 2.8 billion miles from Earth. It holds 6.73 ZL of water (mostly ice). (Therefore, the Earth holds only 20% of the volume of water/ice on Triton.) Photos made by Voyager 2 show that Triton has “cryovolcanoes” that spew out water and ammonia.
• Dione – Dione is a small, icy moon of Saturn. Scientists determined in 2016 that — like Enceladus — Dione likely has a subsurface ocean containing 0.47 ZL of water/ice. (This is 35% of the water volume found on Earth.)
• Pluto – Pluto is the famous planet of yesteryear that astronomers agreed to demote to a dwarf planet. NASA’s New Horizons spacecraft recently helped determine that Pluto has a liquid ocean packed with ammonia at a volume of 4.3 ZL. (So the Earth holds only 31% of the volume of water/ice that is on Pluto.)
• Europa – Europa is the smallest of the four moons of Jupiter and is about the size of Earth’s moon. It likely has a huge, salty ocean containing 2.91 ZL in volume, and shoots jets of its ocean water into space. (So the Earth contains about 46% of the volume of water on Europa.)
• Callisto – Callisto, the second-largest moon of Jupiter, is covered in ice, and almost certainly has a vast ocean with a volume of 19.3 ZL. (The Earth contains only about 7% of the water on Callisto.) However, Callisto’s crust is about 125 miles thick which makes it very difficult for scientists to discover what’s going on down there.
• Titan – Titan is the largest moon of Saturn and the second-largest moon in the solar system. Scientists often refer to it as a “proto-Earth” due to its composition and size. A similarly colossal ocean of liquid water may exist below its roughly 60-mile-thick crust of ice, with a total volume of 31.3 ZL. (The Earth’s water volume is only about 4% of the volume of water/ice on Titan.)
• Ganymede – Ganymede is the largest of Jupiter’s Galilean moons, and the biggest moon in the solar system. Its stores of water amount to 52.7 ZL. (So the Earth’s water volume is only 2.5% of that on Ganymede.)
Scientists recently found even more evidence that Jupiter’s icy moon Europa is hiding an enormous ocean of saltwater.
To say Europa’s ocean is vast would be an understatement. If all of Earth’s water — oceans, lakes, rivers, rain, clouds, and more — were combined into one blob, it’d be just half as large as Europa’s liquid reservoir. (And Europa is about the size of Earth’s moon.)
Scientists think Europa’s ocean might even be habitable to alien life.
“If there’s life at Europa, it’d almost certainly be an independently evolved form of life,” Bob Pappalardo, a planetary scientist at NASA’s Jet Propulsion Laboratory, previously told Business Insider. “Would it use DNA or RNA? Would it use the same chemistry to store and use energy? Discovering extraterrestrial life would revolutionize our understanding of biology.”
But Europa is just one of many ocean worlds in the solar system, including Enceladus, Pluto, Titan, and Ganymede.
To figure out how much liquid water and ice these worlds have compared to Earth, Business Insider contacted Steve Vance, a planetary scientist at NASA’s Jet Propulsion Laboratory. Vance closely monitors research about ocean worlds to create estimates of ice thickness, ocean depth, and other parameters.
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